1. Field of the Invention
The invention relates to emergency call service capabilities, and in particular, to determining the location of callers obtaining emergency call services.
2. Description of the Prior Art
Emergency service call handling capabilities are offered by most telecommunication service providers. For example, users of plain old telephone service (POTS) are typically accustomed to dialing 911 for emergency service. In addition to connecting the user to a public service answering point (PSAP), emergency service call handling capabilities include additional capabilities, such as determining the location of a caller.
Recent advances in telecommunication technologies have made the task of determining the location of a caller more difficult than in the past. In past circuit switched networks, the location of a caller could be easily determined by performing a database look-up to a table holding the calling number stored in association with a physical address. In contrast, new types of voice service technologies do not always associate calling numbers with physical addresses. For example, voice over Internet protocol (VoIP) service users are able to roam wherever there is adequate Internet access. As a result, the location of VoIP callers cannot be reliably determined.
In one prior art solution to the problem of determining the location of VoIP callers, a static relationship is assumed between the calling number and the physical location of the caller. However, this solution only suffices in cases where users are not able to port their phones to new locations.
In another prior art solution, a central server system in a local area network (LAN) actively searches for new VoIP phones. Upon determining a new phone, the central server system queries the switch element closest to the phone for the identity of the switch element. The central server system then determines the approximate location of the phone based on the location of the switch element. Unfortunately, such a solution requires the central server system to have visibility into the network and the ability to query switch elements. In addition, such a solution places an added processing burden on the central server system beyond its regular call processing responsibilities.